简介:Agroupofprojectionweldingexperimentsandjointstension-sheartestsarecarriedoutforcold-rolledsteelsheets,galvanizedsteelsheets(GSS)withouttreatment,GSSwithphosphatingandGSSwithsurfacegreasing,respectively.Theexperimentalresultsareregressivelyanalyzedonthecomputers,thentheprojectionweldedjointtension-shearstrengthcurveandtheperfectweldingcurrentsrangeofeachmaterialareobtained.Theresultsshowthatsurfacetreatmentsofgalvanizedsteelshaveeffectsontheirspotweldabilities.Amongthefourkindsofmaterials,GSSwithsurfacegreasinghavetheworstspotweldability,fortheyneedhigherweldingcurrentandhaveanarrowweldingcurrentrange.
简介:BasemetalsofdomesticpipelinesteelswereusedtostudytheeffectofMnoncorrosionpropertiesofSSCC(SulfideStressCorrosionCracking),andweldswerecarriedouttostudytheeffectofMnSoncorrosionpropertiesofHIC(HydrogenInducedCracking)bothinsolutionswithwethydrogensulfide(H2S).TheywererespectivelyconductedbyreferringtothestandardsofSSCCandHIC.TestingresultsrevealedthatwiththeincreaseofcontentMn,theresistanceofSSCCwillbedecreased,fromthepointofmetallurgicview,anditisMnelementnotCelementtoleadtothetestingresultsofSSCC.Meanwhile,evenundertheconditionwithoutinclusionsMnS,HICinweldsstilloccurred.Thatistosay,MnSisnotnecessaryforHIC,thepresenceoflocalbandedstructuresinwhichMnandPareinclinedtoaggregatecausetothephenomenaofHIC.
简介:Amodelwasdevelopedtosimulatethetemperaturedistributionandnuggetformationduringresistancespotwelding(RSW)ofzinc-coatedsteels.Itemploysacoupledthermal-electrical-mechanicalanalysissimulatingthedynamicRSWprocess.Temperature-dependentthermal-electrical-mechanicalmaterialpropertieswereconsideredincludingcontact-resistance.Thecontactareawasdeterminedfromacoupledthermal-mechanicalanalysis.Alayeroftransitionelementswasusedtorepresentthechangeofcontactareabykillingoractivatingelements.Theheatgenerationandtemperaturefieldwerecomputedinacoupledthermal-electricalmodel.Alltheseanalysesweresolvedusingthecommercialfiniteelementmethod(FEM)basedonANSYScode,andsomeadvancedfunctionswereusedbywritingaparagraphofcodesbytheauthors.Comparedwiththeresultsfromonlycoupledthermal-electricalmodelinwhichcontactareawasuniformduringthewholeprocess,theresultmatchesbettertotheexperimentalresults.
简介:Inthisstudy,atwo-stepheatingprocessisintroducedfortransientliquidphase(TLP)diffusionbondingforsoundjointswithT91heatresistantsteels.Atfirst,ashort-timehighertemperatureheatingstepisaddressedtomelttheinterlayer,followedbythesecondsteptocompleteisothermalsolidificationatalowtemperature.Themostcriticalfeatureofournewmethodisproducinganon-planarinterfaceattheT91heatresistantsteelsjoint.WeproposeatransitionalliquidphasebondingofT91heatresistantsteelsbythisapproach.Sincejointmicrostructureshavebeenstudied,wetestedthetensilestrengthtoassessjointmechanicalproperty.Theresultindicatesthatthesolidifiedbondmaycontainaprimarysolid-solution,similarcompositiontotheparentmetalandfreefromprecipitates.Jointtensilestrengthofthejointisnotlowerthanparentmaterials.Jointbend'sstrengthsareenhancedduetothehighermetal-to-metaljunctionproducinganon-planarbondlines.Nevertheless,thetraditionaltransientliquidphasediffusionbondingproducesplanarones.Bondingparametersofnewprocessare1260℃for0.5minand1230℃for4min.
简介:Thesegregationanddiffusionofboronduringheattreatmentswerestudied.Theinfluenceofboroncontents,agingtimeandappliedstressonFeMo2B2formationwasalsostudied.Finally,theeffectsofboroncontentsandFeMo2B2formationonthehightemperaturestrengthwerestudied.Boronatomsweresegregatedtoprioraustenitegrainboundaryduringnormalizingtreatment.Andtheseboronatomswereslowlydiffusedintothegraininteriorduringtemperingandagingat700℃.TheFeMo2B2phasewasonlyformedafter1,000hagingat700℃inalloycontaining196ppmboron.TheformationofFeMo2B2phaseisacceleratedbytheappliedstress.ItwasexpectedthattheformationofFeMo2B2iscloselyrelatedtotheredistributionofboronatoms.Thetensilestrengthsat700℃areincreasedwiththeincreaseofboroncontents.However,theformationofFeMo2B2phaseresultsinlowertensilestrength.